TNT equivalency method in confined space based on steel plate deformation

•Water mist and nitrogen environment suppress energy release of detonation product.•Structural deformation can be a comprehensive gauge of shock wave intensity.•Unknown energy release process of explosives misguides TNT equivalency.•TNT equivalency method based on response apply to the confined explosion problem. TNT equivalency has been a widely accepted concept in engineering. However, as a fuel-rich explosive, the afterburning effect of detonation products would be remarkable when TNT is detonated in a confined space. The additional energy release from the burning of detonation products makes the traditional TNT equivalency to be more complicated. In this paper, in order to reveal the influence of afterburning effect of detonation products under the condition of confined blast, a series of TNT detonation tests in a confined chamber filled with four different atmospheres, air, nitrogen, water mist, and combined nitrogen and water mist were performed. The temperature, pressure-time histories and deflection of blast loaded steel plate were recorded. It is found that the pressure, temperature and the dynamic response of the blast loaded plate in nitrogen and water mist atmosphere were significantly lower than those in the air conditions, due to different mechanisms of energy release and absorption. In addition, the relation between deflection of target plate and the released energy from explosive was established. Furthermore, the method of determining TNT equivalency in confined explosion considering the afterburning effect was proposed and was employed to determine the TNT equivalency of a cased charge. By comparing the present TNT equivalency method with the method based on quasi-static pressure, the potential application of the method has been illustrated. [Display omitted]